# define _CRT_SECURE_NO_WARNINGS 1
# include<stdio.h>
int main()
{
	int i = 0;
	double sum1 = 0, sum2 = 0;
	for (i = 1; i < 100; i++)
	{
		if (i % 2 == 0)
		{
			
				sum1 = - (sum1 + (1 / i));
		}
		else
		{
			
				sum2 = sum2 + (1 / i);
		}
	}
	printf("%lf", sum1 + sum2);



	return 0;
}